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Question 1. Compare the roles of chloroplasts and mitochondria in eukaryotic cells. [2]

Question 2. Timothy observes a cell through a microscope connected to a monitor. The image on the screen is 3 cm, while the actual size of the cell is 6 μm. Find the magnification of the microscope. [2]

Question 3. Janice increased the oxygen concentration of a solution with yeast cells. Discuss the immediate change in diffusion. Assume that the yeast cells had no oxygen. [2]

Question 4. After submerging a potato in distilled water for 30 minutes, its mass increased from 50 g to 57 g. Calculate the percentage change in mass. [1]

Question 5. Calculate the rate of an enzyme-catalysed reaction if 0.25 moles of a substrate convert to products in 10 minutes. Provide your answer in mol/min. [1]

Question 6. Describe the impact of neutral mutations. [2]

Question 7. Explain the function of spindle fibres during cell division. [2]

Question 8. Name three factors that could increase the risk of cancer. [3]

Question 9. Describe how to prepare a sterile Petri dish for culturing microorganisms. [3]

Question 10. Evie applied antibiotics to disinfect a Petri dish for culturing gut bacteria. Explain why the dish did not have any live bacteria after a week. [1]

Question 11. Explain how antigens help phagocytes remove pathogens. [3]

Question 12. Explain the importance of early detection of HIV. [2]

Question 13. Name the property that makes monoclonal antibodies effective in both therapy and diagnosis. [1]

Question 14. Compare the amount of energy produced in aerobic versus anaerobic respiration. [1]

Question 15. Describe the role of photosynthesis in regulating carbon dioxide levels in the atmosphere. [1]

Question 16. Compare the effects of increasing light intensity and temperature on the photosynthesis rate. [3]

Question 17. Victoria transfers her tomato plant from a cold, humid bedroom to a sunny, warm balcony. How will this change impact the plant's transpiration rate? [1]

Question 18. Name the tissue responsible for transporting organic compounds in plants. [1]

Question 19. A farmer has observed that some crop plants are shorter than others. Suggest a possible group of hormones responsible for the outcome. [1]

Question 20. Describe how auxins relate to gravitropism. [2]

Question 21. Compare the symptoms of a plant deficient in nitrate ions and one deficient in magnesium ions. [2]

Question 22. Ethan is a rower. Explain why during the training, his heart beats faster. [1]

Question 23. Explain the importance of reflex arc in protecting health. [2]

Question 24. Describe the process of accommodation in the eye. [3]

Question 25. How many chambers does a human heart have? [1]

Question 26. Compare the structures of arteries, capillaries, and veins. [3]

Question 27. A community centre is organising a health fair to promote cardiovascular health. Suggest activities and workshops they could include to educate attendees about CVD prevention. [3]

Question 28. Name two diseases that excessive alcohol consumption can cause. [2]

Question 29. Describe the role of proteases. [1]

Question 30. Provide two factors regulated by homeostasis. [2]

Question 31. Name two hormones that control blood glucose levels. [2]

Question 32. In the proximal convoluted tubule, approximately 75% of the filtrate gets reabsorbed into the blood. Discuss the importance of this process. [2]

Question 33. Explain why a zygote could not form from just an ovum. [1]

Question 34. Name two female secondary sexual characteristics influenced by oestrogen. [2]

Question 35. In a breed of cats, the gene for coat colour has two alleles: S for a solid colour (dominant) and s for striped (recessive). Grace crosses a heterozygous solid-coloured cat with a striped cat. Determine the expected ratios of genotypes and phenotypes of their offspring. [2]

Question 36. Suggest a health issue in dogs that selective breeding may result in. [1]

Question 37. Explain how pharmaceutical companies use bacteria to produce diabetes treatment. [2]

Question 38. Name three factors that could decrease energy transfer efficiency between trophic levels in a food chain. [3]

Question 39. Name the levels of biological organisation. [5]

Question 40. Describe how natural selection could lead to the development of long necks in giraffes. [6]

Question 41. Explain how the fossil record provides evidence for the theory of evolution. [3]

Question 42. Discuss the potential long-term impact of overfishing in the context of biodiversity. [4]

Question 43. Describe how increasing temperature changes the decomposition of apples. [3]

Question 44. Provide the roles of fossil fuels in the carbon cycle. [2]

Question 45. Name the primary human activities responsible for increased atmospheric methane and carbon dioxide concentrations. [2]

Question 46. Suggest how unsustainable farming practices might affect land productivity. [2]

Question 47. Provide the steps and results for the Biuret test. [3]

Question 48. Outline the aims of clinical trials in drug development. [3]

Question 49. What is the main compound stored in vacuoles? [1]

Question 50. Provide examples of how microscopy techniques have influenced our understanding of cell structure. [2]

Question 51. Describe how the structure of alveoli contributes to efficient gas exchange. [4]

Question 52. Describe how osmosis affects plant cells. [3]

Question 53. Jason tests the enzyme's activity at pH 6.8 and 7.2. Calculate the percentage change in enzyme activity when moving from pH 6.8 to pH 7.2. Relative activities are 80 units and 100 units respectively. [2]

Question 54. Describe the role of DNA within living organisms. [1]

Question 55. Explain the role of mitosis in living organisms. [2]

Question 56. Charlie investigates the effect of a potential carcinogen on barley sprout cell growth. Which of the following are not control variables?

final sprout height, temperature, humidity, exposure to carcinogen, light, barley species [2]

Question 57. Name the main components of agar medium. [3]

Question 58. Discuss how bacteria resistant to antibiotics develop. [3]

Question 59. Name two main types of cells participating in the immune response.  [2]

Question 60. Provide two main messages that health boards could promote about the prevention of HIV. [2]

Question 61. Explain how monoclonal antibodies can be helpful in diagnosis. [2]

Question 62. Provide the equation for aerobic respiration. [1]

Question 63. Which organelle is responsible for photosynthesis? [1]

Question 64. Henry has doubled the carbon dioxide concentration in a tomato greenhouse, and the harvest has doubled. Provide a reason why the yield of tomatoes will not increase indefinitely with an increasing concentration of carbon dioxide. [1]

Question 65. Describe how temperature affects the rate of transpiration in plants. [1]

Question 66. Name two types of vessels that transport most of the matter in an oak tree. [2]

Question 67. Describe the symptoms of the Tobacco Mosaic Virus on infected plants. [1]

Question 68. Describe the process of phototropism. [2]

Question 69. Explain why magnesium ions are essential for plants. [2]

Question 70. Describe the impact of exercise on the consumption of glucose. [1]

Question 71. Describe the transmission of signals in a typical nervous system. [3]

Question 72. Samuel has myopia (short-sightedness) which is difficulty focusing on distant objects. Suggest a reason for this issue based on the structure of the eye. [2]

Question 73. Which organ does blood from the right ventricle go to? [1]

Question 74. Provide the role of haemoglobin in red blood cells. [1]

Question 75. Name the lifestyle risk factors of cardiovascular diseases. [3]

Question 76. Name a disease that obesity links to. Do not mention any cardiovascular diseases in your answer. [1]

Question 77. Outline the functions of pancreatic lipase and bile. [3]

Question 78. Provide the function of thyroxine in the human body. [1]

Question 79. A nurse is supervising a patient with type 2 diabetes. Describe the lifestyle changes they might recommend to help manage the patient's condition. [3]

Question 80. Explain the process of ultrafiltration in nephrons. [3]

Question 81. What is a haploid cell? [1]

Question 82. In the context of IVF treatment, describe the role of a synthetic version of LH. [2]

Question 83. Describe polygenetic inheritance. [1]

Question 84. Describe the selective breeding of plants. [2]

Question 85. Explain the function of vectors in genetic modification. [2]

Question 86. Predict the impact on a biomass pyramid if a significant percentage of primary consumers in an ecosystem were to die suddenly. [1]

Question 87. Describe how herbivores link with other organisms in an ecosystem. [3]

Question 88. Charles Darwin observed different finch species on the Galápagos Islands. Explain how these observations supported his theory of evolution by natural selection. [4]

Question 89. Provide three examples of fossils. [3]

Question 90. Name the two domains of single-celled organisms. [2]

Question 91. Why do dried fruits stay fresh longer? [2]

Question 92. Abigail has planted beans in her garden. Explain their impact on the carbon cycle. [3]

Question 93. Suggest how the greenhouse effect can affect polar bears in areas full of ice and snow. [2]

Question 94. Explain how climate change can impact global food security. [2]

Question 95. Compare the structures of lipids and proteins. [2]

Question 96. Describe the reasons behind preclinical testing in the drug development process. [2]

Question 97. Name the structure pointed at in the image provided. [1]

Question 98. Convert 275 nm to meters. [1]

Question 99. Describe the structure of the human breathing system. [3]

Question 100. Predict what would happen to red blood cells in a highly concentrated salt solution. [3]

Answer 1. Compare the roles of chloroplasts and mitochondria in eukaryotic cells. [2]

Chloroplasts and mitochondria play critical roles in energy production in eukaryotic cells, but they are responsible for different processes. Chloroplasts convert light energy into chemical energy through photosynthesis, while mitochondria generate ATP through cellular respiration. Chloroplasts contain chlorophyll and are found only in plant cells, while mitochondria are in all eukaryotic cells.

[1 mark] chloroplasts: photosynthesis
[1 mark] mitochondria: ATP/energy generation or respiration

Answer 2. Timothy observes a cell through a microscope connected to a monitor. The image on the screen is 3 cm, while the actual size of the cell is 6 μm. Find the magnification of the microscope. [2]

The formula for magnification is magnification = image size ÷ actual size. In this case, the image size is 3 cm, which needs to be in metres before proceeding with the calculation. Since there is 100 cm in 1 metre, 3 cm equals 0.03 metres. The cell's actual size is 6 μm, equal to 6 × 10⁻⁶ metres. Substituting these values into the formula gives us: magnification = 0.03 m ÷ (6 × 10⁻⁶) m magnification = 5000. Therefore, the magnification of the microscope is 5000x.

[2 marks] 5000(x)
[1 mark] 6 × 10⁻⁶ or 0.03

Answer 3. Janice increased the oxygen concentration of a solution with yeast cells. Discuss the immediate change in diffusion. Assume that the yeast cells had no oxygen. [2]

Increasing the oxygen concentration in a solution will increase the concentration gradient between the solution and the yeast cells. Thus, the diffusion rate will increase.

[1 mark] higher concentration difference
[1 mark] faster diffusion

Answer 4. After submerging a potato in distilled water for 30 minutes, its mass increased from 50 g to 57 g. Calculate the percentage change in mass. [1]

Percentage change = (final mass − initial mass) / initial mass × 100%. In this case, the initial mass of the potato was 50 g, and the final mass was 57 g. Percentage change = (57 − 50) / 50 × 100%, percentage change = 14%.

14%

Answer 5. Calculate the rate of an enzyme-catalysed reaction if 0.25 moles of a substrate convert to products in 10 minutes. Provide your answer in mol/min. [1]

We can use the formula: rate = amount of substrate converted / time. In this case, 0.25 moles of substrate convert to products in 10 minutes. So, the rate is 0.25 moles / 10 minutes = 0.025 moles per minute.

0.025 (mol/min)

Answer 6. Describe the impact of neutral mutations. [2]

Neutral mutations are changes in DNA that do not affect an organism's fitness and can accumulate in a population over time, providing a source of genetic variation essential for evolution. Neutral mutations can increase the diversity of a population and allow for the emergence of new traits.

[1 mark] no effect on fitness
[1 mark] increased genetic variation

Answer 7. Explain the function of spindle fibres during cell division. [2]

Spindle fibres play a crucial role during cell division in mitosis. When the chromosomes align in the middle of the cell, spindle fibres extend from the cell's poles to the chromosomes. These fibres attach to the chromosomes and pull the sister chromatids apart, ensuring that each daughter cell receives an equal set of genetic material. The proper functioning of spindle fibres is critical for maintaining genetic stability and ensuring the correct distribution of chromosomes in the new cells.

[1 mark] attach to chromosomes
[1 mark] pull sister chromatids apart

Answer 8. Name three factors that could increase the risk of cancer. [3]

Three factors that could increase cancer risk include inherited genetic mutations, carcinogen exposure, and lifestyle choices. Inherited genetic mutations can predispose individuals to develop cancer by affecting the normal functioning of genes that regulate cell growth. Exposure to carcinogens can damage cells' DNA and increase the likelihood of cancerous growth. Lifestyle choices, like poor diet, obesity, and excessive sun exposure, can also contribute to cancer development by increasing the risk of DNA damage or promoting cell growth.

[1 mark] inherited genetic mutations
[1 mark] carcinogen exposure
[1 mark] lifestyle choices

Answer 9. Describe how to prepare a sterile Petri dish for culturing microorganisms. [3]

To prepare a sterile Petri dish for culturing microorganisms, first, we ensure that your hands are clean and that you wear gloves. Open the Petri dish in a sterile environment or a laminar flow cabinet, if available. We pour the sterile agar medium into the dish, close the lid, and allow the agar to solidify. We always use sterilised equipment, such as forceps and pipettes, to transfer the microorganisms onto the dish. We keep the dish sealed until we can use it for culturing.

[1 mark] clean hands
[1 mark] wearing gloves
[1 mark] sterilised equipment
[1 mark] sterile agar medium

Answer 10. Evie applied antibiotics to disinfect a Petri dish for culturing gut bacteria. Explain why the dish did not have any live bacteria after a week. [1]

When Evie applied antibiotics to the Petri dish for culturing gut bacteria, the antibiotics killed or inhibited the growth of the live bacteria present. As a result, no live bacteria could grow and reproduce in the dish after a week. This outcome demonstrates the effectiveness of antibiotics in eliminating or inhibiting bacterial growth.

bacteria killed by antibiotics

Answer 11. Explain how antigens help phagocytes remove pathogens. [3]

Antigens, found on the surface of pathogens, help phagocytes remove pathogens by allowing B cells to produce antibodies that specifically recognise and bind to the pathogen. Antibodies bound to the antigens signal other immune cells, including phagocytes, to destroy the pathogen or neutralise its harmful effects. This coordination helps to ensure a powerful and effective immune response against various pathogens.

[1 mark] binding to antigens/pathogens
[1 mark] signalling phagocytes
[1 mark] destroying/neutralising pathogens

Answer 12. Explain the importance of early detection of HIV. [2]

Early detection of HIV allows for timely treatment using antiretroviral therapy (ART), which helps control the virus and prevents its progression to AIDS. This approach improves the individual's quality of life and health prognosis, as the immune system remains relatively intact and better equipped to fight off infections.

[1 mark] timely treatment
[1 mark] AIDS prevention

Answer 13. Name the property that makes monoclonal antibodies effective in both therapy and diagnosis. [1]

The property that makes monoclonal antibodies effective in both therapy and diagnosis is their incredible specificity. It allows them to bind to specific antigens on the surface of harmful cells or pathogens, enabling targeted approaches in both diagnosis and treatment.

specificity

Answer 14. Compare the amount of energy produced in aerobic versus anaerobic respiration. [1]

Aerobic respiration produces more ATP than anaerobic respiration. Aerobic respiration produces a net of 36-38 ATP molecules per glucose molecule. In contrast, anaerobic respiration produces only 2 ATP molecules per glucose molecule. This difference in ATP production is because aerobic respiration can fully oxidise glucose, while anaerobic respiration cannot.

E(aerobic) > E(anaerobic)

Answer 15. Describe the role of photosynthesis in regulating carbon dioxide levels in the atmosphere. [1]

Photosynthesis plays a vital role in regulating carbon dioxide levels in the atmosphere. During photosynthesis, plants and algae take carbon dioxide from the atmosphere to produce glucose and oxygen. Reducing carbon dioxide in the atmosphere helps regulate the Earth's climate.

removing carbon dioxide

Answer 16. Compare the effects of increasing light intensity and temperature on the photosynthesis rate. [3]

Increasing light intensity and temperature both increase the rate of photosynthesis up to a certain point. Beyond this point, the rate levels off due to other limiting factors. However, the increasing light intensity has a more direct effect, increasing the energy available for the light-dependent reactions. Temperature affects the activity of the enzymes involved in the light-independent reactions, and too high or too low temperatures can reduce the rate of photosynthesis.

[1 mark] potential increase for both
[1 mark] plateau at some light intensity
[1 mark] decrease at higher temperature

Answer 17. Victoria transfers her tomato plant from a cold, humid bedroom to a sunny, warm balcony. How will this change impact the plant's transpiration rate? [1]

When Victoria transfers her tomato plant from a cold, humid bedroom to a sunny, warm balcony, the transpiration rate in the plant will likely increase. The warmer temperature on the balcony will cause water molecules to evaporate more quickly, and the increased sunlight will prompt the stomata to open wider for more carbon dioxide absorption, contributing to a higher transpiration rate.

increase

Answer 18. Name the tissue responsible for transporting organic compounds in plants. [1]

Phloem is responsible for transporting organic compounds in plants.

phloem

Answer 19. A farmer has observed that some crop plants are shorter than others. Suggest a possible group of hormones responsible for the outcome. [1]

The farmer's observation of shorter crop plants may be due to a deficiency in gibberellins, as these hormones play a crucial role in promoting stem elongation and overall plant growth.

gibberellins

Answer 20. Describe how auxins relate to gravitropism. [2]

Auxins are involved in gravitropism by regulating the growth and orientation of plant roots and shoots in response to gravity. They accumulate on the lower side of the root or shoot, causing differential growth, which results in the proper orientation of the plant, with roots growing downwards and shoots growing upwards.

[1 mark] differential growth
[1 mark] proper plant orientation

Answer 21. Compare the symptoms of a plant deficient in nitrate ions and one deficient in magnesium ions. [2]

The symptoms of nitrate ion deficiency and magnesium ion deficiency in a plant differ primarily in the pattern of chlorosis. In nitrate ion deficiency, the plant's leaves uniformly turn yellow. On the other hand, in magnesium ion deficiency, chlorosis appears between the veins of the leaves, causing them to look yellow, while the veins themselves stay green.

[1 mark] nitrate ion deficiency: yellowing leaves
[1 mark] magnesium ion deficiency: yellowing between leaf veins

Answer 22. Ethan is a rower. Explain why during the training, his heart beats faster. [1]

As Ethan trains and rows, his body requires more energy and oxygen to fuel the working muscles. His heart rate escalates to pump blood more rapidly to meet this increased demand. Accelerated blood flow transports oxygen and nutrients to his hardworking muscles while also removing waste products. Therefore, during his rowing training, Ethan's heart beats faster to cater to the heightened need for oxygen and energy and to maintain efficient waste removal.

higher oxygen/energy demand

Answer 23. Explain the importance of reflex arc in protecting health. [2]

The reflex arc is essential for protecting health because it enables fast and automatic responses to potentially harmful stimuli. By bypassing the brain, the reflex arc allows for quicker reactions, helping to prevent injuries and maintain overall well-being.

[1 mark] rapid response
[1 mark] preventing injury

Answer 24. Describe the process of accommodation in the eye. [3]

The eye needs to change focus to see objects clearly at different distances. This process, called accommodation, involves the ciliary muscles and the suspensory ligaments surrounding the lens. When focusing on a near object, the ciliary muscles contract, loosening the suspensory ligaments and making the lens more rounded. In contrast, when focusing on a distant object, the ciliary muscles relax, the suspensory ligaments tighten, and the lens flattens. These lens shape alterations enable the eye to focus light precisely onto the retina.

[1 mark] ciliary muscles contraction/relaxation
[1 mark] lens becoming rounded/flatter
[1 mark] near/distant focus

Answer 25. How many chambers does a human heart have? [1]

The human heart has four chambers: two atria and two ventricles.

4

Answer 26. Compare the structures of arteries, capillaries, and veins. [3]

Arteries have thick walls, enabling them to transport oxygenated blood under high pressure from the heart to the rest of the body. Capillaries, the smallest blood vessels, possess thin walls and an extensive network, allowing the exchange of materials between blood and tissues. Veins have thinner walls and carry deoxygenated blood back to the heart, with valves preventing backflow.

[1 mark] arteries: thick walls
[1 mark] capillaries: thin walls
[1 mark] veins: valves

Answer 27. A community centre is organising a health fair to promote cardiovascular health. Suggest activities and workshops they could include to educate attendees about CVD prevention. [3]

The community centre could organise activities and workshops focused on CVD prevention, such as a. Nutrition workshops to teach attendees about the importance of a balanced diet, including meal planning, healthy recipes, and cooking demonstrations. b. Exercise classes or demonstrations to encourage regular physical activity, offering options for various fitness levels and age groups. c. Smoking cessation support groups or resources to help smokers quit and learn about the benefits of being smoke-free for their heart health. d. Alcohol awareness sessions to educate attendees about the risks of excessive alcohol consumption and strategies for limiting intake. e. Stress management workshops to address the impact of stress on heart health and provide techniques for relaxation and stress reduction. 

[1 mark] nutrition workshops
[1 mark] exercise classes
[1 mark] smoking cessation support
[1 mark] alcohol awareness sessions
[1 mark] stress management workshops

Answer 28. Name two diseases that excessive alcohol consumption can cause. [2]

The liver removes toxins from the blood. Alcohol abuse directly contributes to liver diseases such as alcoholic hepatitis, fatty liver and cirrhosis.

[1 mark] hepatitis
[1 mark] fatty liver
[1 mark] cirrhosis

Answer 29. Describe the role of proteases. [1]

Proteases play a vital role in protein digestion. They begin their work in the stomach, where pepsin, a type of protease, cuts long chains of amino acids into shorter segments called peptides. Proteases like trypsin and chymotrypsin further break down these peptides into individual amino acids. These amino acids are then ready for absorption by the body.

breaking down proteins

Answer 30. Provide two factors regulated by homeostasis. [2]

Homeostasis revolves around the body's ability to preserve a delicate balance, allowing cells and organs to function optimally. In humans, it involves the regulation of various factors, including blood sugar levels, water content, and body temperature. The latter, thermoregulation, is crucial as it ensures that enzymes work efficiently and metabolic processes occur smoothly.

[1 mark] blood sugar
[1 mark] water
[1 mark] pH
[1 mark] temperature

Answer 31. Name two hormones that control blood glucose levels. [2]

Insulin and glucagon are the two hormones responsible for controlling blood glucose levels.

[1 mark] insulin
[1 mark] glucagon

Answer 32. In the proximal convoluted tubule, approximately 75% of the filtrate gets reabsorbed into the blood. Discuss the importance of this process. [2]

Reabsorption in the proximal convoluted tubule is crucial because it allows the body to recover approximately 75% of the filtrate, including valuable substances like glucose, amino acids, and ions. Water follows these substances back into the bloodstream via osmosis, ensuring that the body retains essential nutrients and maintains proper hydration.

[1 mark] recovering glucose/amino acids/ions
[1 mark] osmosis returning water to bloodstream

Answer 33. Explain why a zygote could not form from just an ovum. [1]

A zygote cannot form from just an ovum because it requires the genetic material from both a spermatozoon and an ovum. This combination ensures that the zygote has the full complement of chromosomes necessary for proper development.

It lacks genetic material from spermatozoon.

Answer 34. Name two female secondary sexual characteristics influenced by oestrogen. [2]

Two female secondary sexual characteristics influenced by oestrogen are the growth of breasts and the widening of hips. These characteristics develop due to the hormone's influence on fat distribution and the growth of specific tissues in the female body.

[1 mark] breast growth
[1 mark] hip widening

Answer 35. In a breed of cats, the gene for coat colour has two alleles: S for a solid colour (dominant) and s for striped (recessive). Grace crosses a heterozygous solid-coloured cat with a striped cat. Determine the expected ratios of genotypes and phenotypes of their offspring. [2]

When Grace crosses a heterozygous solid-coloured cat (Ss) with a striped cat (ss), we can use a Punnett square to calculate their offspring's genotypic and phenotypic ratios. The resulting genotypes are Ss and ss. The genotypic ratio is 1 Ss: 1 ss. As S is dominant, the phenotypic ratio is 1 solid: 1 striped.

[1 mark] genotypic ratio: 1 Ss : 1 ss
[1 mark] phenotypic ratio: 1 solid: 1 striped

Answer 36. Suggest a health issue in dogs that selective breeding may result in. [1]

Selective breeding can result in breathing difficulties in some breeds of dogs when breeders focus on specific physical appearances, such as a flattened face or shortened snout, without considering the potential health implications. Breeding dogs for these physical traits can inadvertently cause structural changes to the respiratory system, leading to conditions like brachycephalic obstructive airway syndrome, which can cause breathing difficulties and other health issues.

breathing difficulties

Answer 37. Explain how pharmaceutical companies use bacteria to produce diabetes treatment. [2]

Scientists have engineered bacteria to produce insulin. These genetically modified bacteria produce insulin, which can be harvested and purified for treating diabetes in humans. This method provides a reliable and efficient way to produce insulin, benefiting people with diabetes who require insulin therapy.

[1 mark] genetic modification
[1 mark] human insulin

Answer 38. Name three factors that could decrease energy transfer efficiency between trophic levels in a food chain. [3]

Respiration losses: Energy used in metabolic processes is not available for transfer. Heat loss: Energy lost as heat during metabolic activities. Incomplete digestion: Not all ingested material is digested and assimilated; some is excreted as waste.

[1 mark] respiration losses
[1 mark] heat loss
[1 mark] incomplete digestion

Answer 39. Name the levels of biological organisation. [5]

Levels of biological organisation include the individual organism, population (organisms of the same species in one area), community (all populations interacting in an area), ecosystem (the community and its abiotic environment), and biosphere (the global collection of ecosystems).

[1 mark] organism
[1 mark] population
[1 mark] community
[1 mark] ecosystem
[1 mark] biosphere

Answer 40. Describe how natural selection could lead to the development of long necks in giraffes. [6]

In a population of giraffes, individuals show variation in neck length due to genetic differences. When food sources like leaves become scarce on lower branches, giraffes must compete for access to leaves found higher up in trees.Giraffes with slightly longer necks gain an advantage because they can reach these food sources more easily, allowing them to survive better during times of scarcity. These giraffes are more likely to reproduce and pass on their genes for longer necks to the next generation. Over many generations, the trait for longer necks becomes more common within the population as it continuously provides a survival benefit.

[1 mark] variation in neck length within the population
[1 mark] competition for food high in trees
[1 mark] longer necks reaching food more easily
[1 mark] longer-necked giraffes surviving/reproduce more
[1 mark] passing on genes for longer necks to offspring
[1 mark] long necks becoming more common over generations

Answer 41. Explain how the fossil record provides evidence for the theory of evolution. [3]

Fossils provide evidence for evolution by showing how species have changed over millions of years. By comparing fossils from different geological layers, scientists observe gradual changes in physical traits, which suggest that species have adapted over time in response to environmental pressures. Fossils of similar structures in different species, such as the pentadactyl limb found in amphibians, reptiles, and mammals, suggest common ancestry. The link supports the idea that present-day species have evolved from earlier forms and that evolution is a gradual change leading to new adaptations and species.

[1 mark] fossil layers showing gradual changes in species over time
[1 mark] similarities in fossil structures suggesting common ancestry
[1 mark] fossils of transitional species showing evolutionary links between groups

Answer 42. Discuss the potential long-term impact of overfishing in the context of biodiversity. [4]

Overfishing can have severe long-term impacts on biodiversity. As we deplete fish stocks to unsustainable levels, the delicate balance of aquatic ecosystems gets disrupted. Over time, this can lead to the extinction of certain fish species, which can impact the species that rely on them for food. It could also allow species lower down the food chain to overpopulate, potentially leading to unexpected changes in the ecosystem.

[1 mark] extinction of species
[1 mark] disrupted food chains
[1 mark] ecosystem imbalance
[1 mark] reduced biodiversity

Answer 43. Describe how increasing temperature changes the decomposition of apples. [3]

Higher temperatures generally speed up decay. However, a temperature that is too high can kill the decomposers.

[1 mark] generally higher rate at higher temperature
[1 mark] high temperatures kill decomposers
[1 mark] no decomposition at high temperatures

Answer 44. Provide the roles of fossil fuels in the carbon cycle. [2]

Fossil fuels serve two primary roles in the carbon cycle. First, they act as long-term storage for carbon. When plants and animals die, some carbon-rich material forms fossil fuels like coal, oil, and natural gas over long periods. Second, when humans burn these fossil fuels for energy, they release the stored carbon back into the atmosphere as carbon dioxide.

[1 mark] carbon storage
[1 mark] CO₂ release via combustion

Answer 45. Name the primary human activities responsible for increased atmospheric methane and carbon dioxide concentrations. [2]

The primary human activities contributing to increased atmospheric methane and carbon dioxide concentrations include burning fossil fuels, deforestation, and agriculture. Fossil fuels, when combusted, emit a significant amount of carbon dioxide into the atmosphere. Deforestation also contributes to carbon dioxide levels as trees, which absorb carbon dioxide for photosynthesis, are cut down, reducing Earth's capacity to absorb the gas. Agriculture, particularly livestock farming, and the decomposition of organic matter, such as in landfills, release methane, another potent greenhouse gas.

[1 mark] burning fossil fuels
[1 mark] deforestation

Answer 46. Suggest how unsustainable farming practices might affect land productivity. [2]

Unsustainable farming practices, such as mono-cropping and overuse of fertilisers, can degrade the soil. It can strip the land of essential nutrients, reducing fertility and productivity. Over time, this can result in less productive farmland, which is less able to support the growth of crops.

[1 mark] soil degradation
[1 mark] nutrient depletion

Answer 47. Provide the steps and results for the Biuret test. [3]

To perform the Biuret test, we prepare a solution containing proteins. Next, we add a few drops of Biuret reagent, a mixture of copper sulphate and sodium hydroxide, to the solution. We observe the colour change. A purple colour indicates the presence of proteins, while a blue colour suggests their absence.

[1 mark] mixing protein solution, Biuret reagent
[1 mark] purple for proteins
[1 mark] blue for absence

Answer 48. Outline the aims of clinical trials in drug development. [3]

Phase I: In this phase, researchers test the drug on a small group for its safety, dosage range, and potential side effects. This initial phase helps to establish whether the drug is safe for humans and identify any adverse effects that may occur. Phase II: Researchers expand the group of participants to include patients with the targeted disease or condition. This phase provides further insight into the drug's efficacy, optimal dosing, and continued safety. During Phase II, the drug's effectiveness is assessed, and researchers can refine dosing regimens for the next phase. Phase III involves large-scale testing with diverse populations to confirm the drug's effectiveness, monitor its side effects, and compare it with existing treatments. Phase III trials provide robust evidence for the drug's safety and efficacy, allowing regulatory authorities to decide whether to approve it for public use.

[1 mark] safety or side effects
[1 mark] efficacy or optimal dosing
[1 mark] comparing treatments

Answer 49. What is the main compound stored in vacuoles? [1]

The primary material stored in vacuoles is water, which helps maintain turgor pressure in plant cells and provides a medium for chemical reactions. Vacuoles also store nutrients and waste products.

water

Answer 50. Provide examples of how microscopy techniques have influenced our understanding of cell structure. [2]

Microscopy techniques have influenced our understanding of cell structure in various ways. For example, discovering organelles such as mitochondria, chloroplasts, and the nucleus was only possible through microscopes. Additionally, the ability to visualise sub-cellular structures such as ribosomes and the cytoskeleton has provided insights into how cells function.

[1 mark] discovering organelles
[1 mark] understanding how cells function

Answer 51. Describe how the structure of alveoli contributes to efficient gas exchange. [4]

Alveoli are small air sacs located at the ends of bronchioles. They have thin walls, just one cell thick, and are surrounded by a dense capillary network. In addition, a moist lining inside the alveoli allows oxygen to dissolve before diffusing across the respiratory membrane and entering the blood. These structural features minimise the distance for gas diffusion and maximise the surface area for oxygen and carbon dioxide exchange, contributing to efficient gas exchange.

[1 mark] thin walls
[1 mark] moist lining
[1 mark] dense capillary network
[1 mark] maximised surface area
[1 mark] minimises diffusion distance

Answer 52. Describe how osmosis affects plant cells. [3]

Osmosis affects plant cells in different ways depending on the concentration of the surrounding solution. Cells placed in concentrated (hypertonic) solutions lose water and shrink. On the other hand, cells in dilute (hypotonic) solutions gain water and swell.

[1 mark] water moving to more concentrated solution
[1 mark] concentrated solution: shrinking
[1 mark] dilute solutions: swelling/turgid

Answer 53. Jason tests the enzyme's activity at pH 6.8 and 7.2. Calculate the percentage change in enzyme activity when moving from pH 6.8 to pH 7.2. Relative activities are 80 units and 100 units respectively. [2]

Moving from pH 6.8 (80 units) to pH 7.2 (100 units) gives ((100 − 80) / 80) × 100 = 25% increase.

[1 mark] 25%
[1 mark] 20

Answer 54. Describe the role of DNA within living organisms. [1]

DNA serves as the genetic blueprint for all living organisms. It carries the information necessary for cell development, growth, reproduction, and functioning. We find DNA in the cell nucleus, which stores and passes on genetic traits from generation to generation.

carrying genetic information

Answer 55. Explain the role of mitosis in living organisms. [2]

Mitosis plays a vital role in the growth and repair of tissues in living organisms. When a cell undergoes mitosis, it divides into two identical daughter cells, each containing the same number of chromosomes as the original cell. This process helps maintain a stable genetic makeup, allowing the organism to generate new cells for growth, repair, and tissue maintenance.

[1 mark] growth
[1 mark] repair of tissues

Answer 56. Charlie investigates the effect of a potential carcinogen on barley sprout cell growth. Which of the following are not control variables?

final sprout height, temperature, humidity, exposure to carcinogen, light, barley species [2]

In Charlie's experiment on the effect of a potential carcinogen on barley sprout cell growth, the control variables are the factors that are kept constant to ensure a fair test. Therefore, the temperature, humidity, light, and barley species should be controlled to prevent them from affecting the results. In this context, the variables that are not control variables are "final sprout height" and "exposure to carcinogen." Final sprout height is the dependent variable, as it is what Charlie is measuring to assess the impact of the carcinogen. Exposure to the carcinogen is the independent variable, which Charlie manipulates to see its effect on sprout height.

[1 mark] final sprout height
[1 mark] exposure to carcinogen

Answer 57. Name the main components of agar medium. [3]

The main components of agar medium include carbohydrates, proteins, vitamins, and minerals. These nutrients provide the necessary resources for microorganisms to grow and multiply.

[1 mark] carbohydrates
[1 mark] proteins
[1 mark] vitamins
[1 mark] minerals

Answer 58. Discuss how bacteria resistant to antibiotics develop. [3]

Bacteria resistant to antibiotics develop through a process of natural selection. When exposed to antibiotics, some bacteria may possess genetic variations that enable them to survive the drug's effects. These surviving bacteria reproduce, passing on their resistance genes to their offspring. Over time, the proportion of resistant bacteria within the population increases, leading to the development of antibiotic-resistant strains.

[1 mark] some surviving antibiotics
[1 mark] natural selection
[1 mark] resistant genes passed on

Answer 59. Name two main types of cells participating in the immune response.  [2]

The two main types of cells participating in the immune response are phagocytes and lymphocytes.

[1 mark] phagocytes
[1 mark] lymphocytes

Answer 60. Provide two main messages that health boards could promote about the prevention of HIV. [2]

Health boards should promote safe sex practices, such as using condoms, getting regularly tested for HIV, and discussing sexual health with partners. Additionally, they should emphasize the need to avoid sharing needles and encourage awareness about HIV transmission routes and early symptoms.

[1 mark] safe sex promotion
[1 mark] avoiding needle sharing

Answer 61. Explain how monoclonal antibodies can be helpful in diagnosis. [2]

Monoclonal antibodies are helpful in diagnosis because they bind with high specificity to unique molecules called antigens found on the surface of cells or pathogens. Scientists can attach a fluorescent dye to the antibodies, enabling them to track the antibodies as they bind to their target antigens. This targeted approach allows for early detection and accurate diagnoses of diseases or infections within a patient's body, ultimately improving treatment outcomes.

[1 mark] binding to specific antigens
[1 mark] attaching fluorescent dye

Answer 62. Provide the equation for aerobic respiration. [1]

The equation for it is glucose + oxygen → carbon dioxide + water + energy (as ATP). This process occurs mainly in eukaryotic cells' mitochondria and prokaryotic cells' cytoplasm.

glucose + oxygen → carbon dioxide + water + energy

Answer 63. Which organelle is responsible for photosynthesis? [1]

The organelle responsible for photosynthesis is the chloroplast. Chloroplasts are specialised organelles found in green plants and some algae cells. They contain pigments, such as chlorophyll, that absorb light energy and use it to drive the process of photosynthesis.

chloroplast

Answer 64. Henry has doubled the carbon dioxide concentration in a tomato greenhouse, and the harvest has doubled. Provide a reason why the yield of tomatoes will not increase indefinitely with an increasing concentration of carbon dioxide. [1]

If Henry keeps increasing the carbon dioxide concentration indefinitely, the yield will eventually reach a point where other factors become limiting, such as light or nutrient availability. The rate of photosynthesis will level off and eventually decrease, leading to a decrease in yield.

other limiting factors

Answer 65. Describe how temperature affects the rate of transpiration in plants. [1]

Temperature affects the rate of transpiration in plants by influencing the evaporation of water molecules. Water molecules evaporate more quickly as temperatures rise, creating a steeper water vapour concentration gradient between the leaf's interior and the atmosphere. This steeper gradient causes water vapour to move out of the leaf more rapidly, increasing the transpiration rate.

higher temperature, faster transpiration

Answer 66. Name two types of vessels that transport most of the matter in an oak tree. [2]

The two primary types of vessels that transport matter in the tree are the xylem and the phloem.

[1 mark] xylem
[1 mark] phloem

Answer 67. Describe the symptoms of the Tobacco Mosaic Virus on infected plants. [1]

When a plant becomes infected with Tobacco Mosaic Virus, its leaves display a mosaic pattern of yellow and green. This pattern results from the virus interfering with the plant's ability to produce chlorophyll, essential for photosynthesis. Consequently, infected plants suffer from reduced growth and productivity.

mosaic pattern of yellow, green

Answer 68. Describe the process of phototropism. [2]

Phototropism is the growth of a plant towards light sources to increase its exposure to sunlight and enhance photosynthetic efficiency. Auxins accumulate on the shaded side of the stem, causing cell elongation, which leads to the bending of the plant towards the light source.

[1 mark] plant bending towards light
[1 mark] auxins causing cell elongation

Answer 69. Explain why magnesium ions are essential for plants. [2]

Magnesium ions are essential for plants because they form the central atom in the chlorophyll molecule. Chlorophyll captures sunlight, which is the energy source for photosynthesis. Without enough magnesium ions, a plant cannot produce sufficient chlorophyll, inhibiting its ability to perform photosynthesis and thus restricting its growth and development.

[1 mark] central atom in chlorophyll
[1 mark] photosynthesis

Answer 70. Describe the impact of exercise on the consumption of glucose. [1]

When we exercise, our muscles require more energy to perform physical activities. The body taps into its stored energy reserves, including glucose, to meet this increased energy demand. The breakdown of glucose through cellular respiration releases energy, which powers the muscles and enables us to perform the exercise. As a result, the more we exercise, the more glucose our body consumes to meet the heightened energy requirements.

increased glucose consumption

Answer 71. Describe the transmission of signals in a typical nervous system. [3]

In a typical nervous system response, signals travel from receptors to the central nervous system, where the brain processes the information and decides on an appropriate response.

[1 mark] from receptors
[1 mark] brain
[1 mark] to effectors

Answer 72. Samuel has myopia (short-sightedness) which is difficulty focusing on distant objects. Suggest a reason for this issue based on the structure of the eye. [2]

Samuel's myopia, or short-sightedness, is likely due to an issue with the shape of his eye or the lens. In individuals with myopia, the eye is often elongated or the lens is too curved. This focusing issue can be corrected using concave lenses in eyeglasses or contact lenses, which help to focus light correctly onto the retina.

[1 mark] lens too curved
[1 mark] light focusing in front of retina

Answer 73. Which organ does blood from the right ventricle go to? [1]

Oxygen-poor blood enters the right atrium before being pumped into the right ventricle. From there, it travels to the lungs to pick up oxygen.

lungs

Answer 74. Provide the role of haemoglobin in red blood cells. [1]

Haemoglobin binds to oxygen and facilitates its transportation throughout the body. This process ensures cells receive the necessary oxygen to function properly and maintain overall health.

binding/transporting oxygen

Answer 75. Name the lifestyle risk factors of cardiovascular diseases. [3]

The risk factors for cardiovascular diseases include unhealthy diets, excessive alcohol consumption, smoking, and high intake of saturated fats, salt, and sugar.

[1 mark] smoking
[1 mark] unhealthy diet
[1 mark] excessive alcohol consumption

Answer 76. Name a disease that obesity links to. Do not mention any cardiovascular diseases in your answer. [1]

Obesity links to type 2 diabetes and cardiovascular diseases.

type 2 diabetes

Answer 77. Outline the functions of pancreatic lipase and bile. [3]

Pancreatic lipase and bile break down fats into fatty acids and glycerol. Pancreatic lipase is responsible for the actual conversion of fats, while bile has two main functions: emulsification and neutralisation. Bile emulsifies fats, breaking them into smaller droplets to increase their surface area, making it easier for lipase to access the fats and work efficiently. Additionally, bile neutralises stomach acid, creating a suitable environment for enzymes in the small intestine.

[1 mark] lipase converting fats to fatty acids, glycerol
[1 mark] bile emulsifying fats
[1 mark] bile neutralising stomach acid

Answer 78. Provide the function of thyroxine in the human body. [1]

Thyroxine is a crucial hormone that the thyroid gland produces to regulate the body's metabolism. The metabolic rate refers to the speed at which cells convert nutrients into energy. By modulating the metabolic rate, thyroxine helps ensure the body has sufficient energy to function optimally.

metabolism regulation

Answer 79. A nurse is supervising a patient with type 2 diabetes. Describe the lifestyle changes they might recommend to help manage the patient's condition. [3]

The nurse might recommend several lifestyle changes to help manage the patient's type 2 diabetes, such as adopting a healthier diet, engaging in regular physical activity, and losing weight if the patient is overweight or obese.

[1 mark] healthier diet
[1 mark] regular physical activity
[1 mark] weight loss

Answer 80. Explain the process of ultrafiltration in nephrons. [3]

Ultrafiltration in nephrons occurs in the Bowman's capsule, where blood flows into the glomerulus, a cluster of tiny blood vessels. High pressure forces water, salts, glucose, and waste products out of the blood and into the capsule while larger proteins and blood cells remain in the blood vessels. This process creates the initial filtrate that will continue through the nephron.

[1 mark] blood flow into glomerulus
[1 mark] high pressure forcing water, salts/glucose, waste into capsule
[1 mark] large proteins, blood cells remaining

Answer 81. What is a haploid cell? [1]

Haploid cells have just half of the genetic material of a typical body cell. Gametes, such as spermatozoa in males and ova in females, are examples of haploid cells.

half of chromosomes

Answer 82. In the context of IVF treatment, describe the role of a synthetic version of LH. [2]

In IVF treatment, healthcare providers use synthetic LH (luteinising hormone) and human chorionic gonadotropin (hCG) to induce ovulation at a specific time. This controlled induction allows doctors to collect the eggs for fertilisation on time, optimising the IVF process and increasing the likelihood of successful conception.

[1 mark] induce ovulation
[1 mark] control egg collection timing

Answer 83. Describe polygenetic inheritance. [1]

Polygenic inheritance occurs when multiple genes determine a single characteristic. Each contributing gene adds to the trait's variance, resulting in a continuous range of phenotypic expressions like human height or skin colour. This complexity ensures a wide variation within a population.

multiple genes for one trait

Answer 84. Describe the selective breeding of plants. [2]

Selective breeding of plants involves choosing plants with specific desirable traits and breeding them together to produce offspring with those traits. Over several generations, the desirable characteristics become more pronounced in the population. For example, farmers might select plants with higher crop yields or drought resistance to develop a generation of plants that can produce more food for a growing population or thrive in challenging environmental conditions.

[1 mark] choosing plants with desirable traits
[1 mark] breeding them together

Answer 85. Explain the function of vectors in genetic modification. [2]

Vectors, such as plasmids, carry foreign DNA in genetic modification. They facilitate the process by allowing the insertion of the desired gene into the vector. Once we insert the gene, the vector can transfer the gene into a host organism, ensuring the new genetic information is in the host organism's DNA.

[1 mark] carriers for foreign DNA
[1 mark] transfer gene into host organism

Answer 86. Predict the impact on a biomass pyramid if a significant percentage of primary consumers in an ecosystem were to die suddenly. [1]

If a significant number of primary consumers die, the immediate effect on the biomass pyramid would be a reduction in the biomass at this trophic level. This reduction would disrupt the food availability for secondary consumers, potentially decreasing their population size over time. Moreover, the biomass of producers might initially increase due to less consumption, but over time, nutrient cycles might be disrupted, affecting the entire ecosystem's health.

decrease in secondary consumer biomass

Answer 87. Describe how herbivores link with other organisms in an ecosystem. [3]

Herbivores connect plants and higher-level consumers by consuming plants and transferring energy to predators, which eat herbivores. Their waste and remains also support decomposers that recycle nutrients back into the ecosystem, sustaining plant growth.

[1 mark] consuming producers
[1 mark] providing energy to carnivores
[1 mark] waste supporting decomposers

Answer 88. Charles Darwin observed different finch species on the Galápagos Islands. Explain how these observations supported his theory of evolution by natural selection. [4]

Darwin noticed that the finches on different islands had varying beak shapes and sizes, which correlated with their specific diets and environments. For instance, finches with strong, thick beaks could crack open large seeds, while those with slender beaks were better suited for catching insects. He deduced that these beak adaptations arose due to the selective pressure of food availability on each island. Finches with beaks that matched the available food source were more likely to survive, reproduce, and pass on their advantageous beak shape to their offspring. Over generations, this led to the emergence of distinct species of finches, each specialised for their specific niche.

[1 mark] beak shapes adapted to different diets
[1 mark] finches with suitable beaks surviving/reproducing more
[1 mark] passing on advantageous beak shape
[1 mark] different beak shapes leading to distinct species

Answer 89. Provide three examples of fossils. [3]

Examples of fossils could be a dinosaur bone that has undergone mineral replacement, a shell trapped in layers of sediment that has hardened into rock, and the imprint of a fern leaf on a sandstone surface. Fossils can also consist of less obvious forms, like the hardened burrows of worms in ancient sea beds or the preserved footprints of a mammal.

[1 mark] bone
[1 mark] shell
[1 mark] imprint

Answer 90. Name the two domains of single-celled organisms. [2]

The two domains of single-celled organisms are Bacteria and Archaea.

[1 mark] Bacteria
[1 mark] Archaea

Answer 91. Why do dried fruits stay fresh longer? [2]

Removing moisture from the fruit inhibits the growth of microorganisms that cause decay. Additionally, drying can also concentrate the sugars in the fruit. Higher sugar concentration creates a hostile environment for microbial growth.

[1 mark] lack of water
[1 mark] high sugar concentration
[1 mark] slow decay

Answer 92. Abigail has planted beans in her garden. Explain their impact on the carbon cycle. [3]

Like all plants, beans have an essential impact on the carbon cycle. Through photosynthesis, they absorb carbon dioxide from the atmosphere and store it in their tissues. When animals or humans eat these beans, they consume the stored carbon. This carbon then returns to the atmosphere as carbon dioxide through respiration.

[1 mark] absorbing CO₂ via photosynthesis
[1 mark] storing carbon
[1 mark] return CO₂ to atmosphere via respiration

Answer 93. Suggest how the greenhouse effect can affect polar bears in areas full of ice and snow. [2]

The greenhouse effect can drastically affect polar bears in snowy and icy regions. As methane and carbon dioxide levels rise, the greenhouse effect intensifies, leading to global warming. This warming results in a higher average temperature on Earth, causing polar ice caps to melt. With the melting of ice and snow, polar bears lose their hunting grounds, which can lead to a decline in their population.

[1 mark] melting ice
[1 mark] loss of hunting grounds

Answer 94. Explain how climate change can impact global food security. [2]

Climate change can lead to extreme weather conditions such as droughts and floods. These conditions can devastate crops, reducing the available food supply. Additionally, more subtle changes in temperature and precipitation patterns can disrupt the growing seasons, making it harder for farmers to plan and grow their crops successfully.

[1 mark] altered weather patterns
[1 mark] extreme weather events
[1 mark] disrupted growing seasons

Answer 95. Compare the structures of lipids and proteins. [2]

Lipids comprise glycerol and fatty acids, with the primary structure being a molecule of glycerol bonded to three fatty acid molecules to form a triglyceride. Proteins consist of amino acids, their monomers, linked together in long chains to form polypeptides. One or more polypeptide chains join together to create a protein.

[1 mark] lipids: glycerol, fatty acids
[1 mark] proteins: amino acids

Answer 96. Describe the reasons behind preclinical testing in the drug development process. [2]

Preclinical testing is crucial in the drug development process as it determines the effectiveness and safety of a compound before it reaches human subjects. This step involves laboratory experiments and animal testing, assessing a compound's efficacy and possible side effects. Preclinical testing allows scientists to understand how the drug works at a molecular level, helping them predict potential risks and make informed decisions about whether to proceed with clinical trials.

[1 mark] assess efficacy
[1 mark] identify side effects
[1 mark] understand molecular interactions

Answer 97. Name the structure pointed at in the image provided. [1]

The structure pointed at in the image is the nucleus.

nucleus

Answer 98. Convert 275 nm to meters. [1]

To convert 275 nm to meters, we can use the standard form of nanometers, which is 10⁻⁹ meters. Therefore, 275 nm is equal to 275 × 10⁻⁹ meters. Simplifying this expression gives us 2.75 × 10⁻⁷ meters.

2.75 × 10⁻⁷ m

Answer 99. Describe the structure of the human breathing system. [3]

The human breathing system comprises the trachea, bronchi, lungs, and alveoli. The trachea branches into two smaller tubes called bronchi, which lead to each lung, supplying them with oxygen. Within the lungs, the bronchi further branch into smaller tubes called bronchioles, creating a vast network that maximises the surface area for gas exchange. Finally, small air sacs called alveoli are at the ends of the bronchioles, where oxygen and carbon dioxide exchange occurs.

[1 mark] trachea
[1 mark] bronchi
[1 mark] lungs

Answer 100. Predict what would happen to red blood cells in a highly concentrated salt solution. [3]

A selectively permeable membrane surrounds red blood cells. When placed in a highly concentrated salt solution, the salt concentration outside the cell is much higher than inside the cell. A hypertonic environment causes water to move out of the cell through osmosis. As a result, the cell loses its water and shrinks.

[1 mark] osmosis
[1 mark] water loss
[1 mark] shrinking

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